My Vaillant ECOmax VUW 286 EH combi condenser is giving central heating but no hot water.
About 8 years old, working fine until early this year when it suddenly stopped supplying HW. Demanding hot water for the shower, kitchen sink and bathroom taps the HW would become tepid but not hot and the radiators would become warm. To get HW you must close the CH valve and switch the boiler to HW only.
A diverter valve problem then? Replaced the diverter valve with a brand new one (£14 on ebay), no change.
A controller board problem then? There are 22 volts DC at the diverter valve solenoid when HW is demanded and enough magnetic force to hold a large screwdriver in place against gravity.
A faulty diaphragm? The diaphragm is new with the valve and I removed the copper pipe which connects the diaphragm to the low pressure side of the pump and it is clear of blockages.
So now I'm stuck, I can't think of what else to try (except email Vaillant, which I just did) any suggestions?